Municipalities, water districts, and other agencies that supply water to consumers sometimes regulate the distribution of water because they have an insufficient supply of water to meet consumer demand, maintain water reserves for fire control, etc. Although, insufficient water supplies may occur anytime during the year, they generally occur during the summer and especially during periods of extended drought that frequently result in low water reserves and higher than normal water demands for irrigation. The primary method used to regulate water distribution is through the use of restrictions on the use of water for irrigation or restricting other outdoor water use, such as, hosing the driveways and washing cars. Restrictions on irrigation include requiring consumers to irrigate only on odd days or even days, irrigate only two times a week instead of daily, and so forth. Various means are used to obtain the irrigation users compliance with the restrictions and may include fines, conservation pricing, education, etc.
As mentioned above, these restrictions are usually imposed when there are extended periods of drought. However, restrictions have been imposed on irrigation applications when there is high usage of water on specific days and even intra-day high water use. For example, irrigations are sometimes restricted to being applied during certain times of the day, such as from 8:00 p.m. to 6:00 a.m. This eliminates the operation of irrigation systems during the day time hours when there is likely higher indoor water use. Setting the irrigation controller to only execute an irrigation application during the evening or early morning hours should reduce the high peak water use values that would have occurred had the irrigations been executed during the daytime hours.
High peak water use values may occur on days following days with extremely hot and dry weather conditions. This occurs because higher irrigation watering amounts generally are applied on days following days with extremely hot and dry weather conditions. This is especially true with controllers that vary irrigation applications based on evapotranspiration (ET controllers). Evapotranspiration rates are closely correlated to the water requirements of plants. Evapotranspiration is the water lost by direct evaporation from the soil and plant and by transpiration from the plant surface. Potential evapotranspiration (ETo) is calculated from meteorological data and the hotter, dryer the weather conditions the higher will be the ETo readings. As ETo rates increase, due to hot, dry weather, the irrigation application watering amounts, applied by ET controllers, will also increase. If there are several ET controllers installed in a water supply area, a high peak water use value could occur on a day following a day with hot, dry weather conditions.
There are several companies that are presently marketing ET controllers or will be in the near future. Irrigation controllers that derive all or part of the irrigation schedule from potential evapotranspiration (ETo) data are discussed in U.S. Pat. No. 5,479,339 issued December 1995, to Miller, U.S. Pat. No. 5,097,861 issued March 1992 to Hopkins, et al., U.S. Pat. No. 5,023,787 issued June 1991 and U.S. Pat. No. 5,229,937 issued July 1993 both to Evelyn-Veere, U.S. Pat. No. 5,208,855, issued May 1993, to Marian, U.S. Pat. No. 5,696,671, issued December 1997, and U.S. Pat. No. 5,870,302, issued February 1999, both to Oliver and U.S. Pat. No. 6,102,061, issued August, 2000 to Addink.
Most of the above ET controllers base application durations on the previous days ETo rates. However, U.S. Pat. No. 5,208,855 discusses an ET controller that schedules irrigation application durations based on an average of the previous weeks ETo data. This generally prevents high water applications being applied on any one day but may also result in irrigations that do not meet the water requirements of the plants. This is especially true, when a cool, wet week is followed by an extremely hot, dry week.
What is needed is an irrigation management system that uses a microprocessor to automatically derive a new irrigation schedule and/or automatically control the water use of other water using devices to reduce the potential of extremely high peak water use values from occurring. Further more, the new irrigation schedules have to meet the water needs of the plants with very little waste of water.